The invention discloses an online analysis method and system of components of shale residual gas and rare gas and relates to an analysis technology of the shale residual gas. The online analysis method comprises the following steps: crushing a sample to be detected into powder at a room temperature and under a vacuum condition, so as to obtain a gas mixture; carrying out oxidization treatment on organic gas in the gas mixture, and removing the organic gas; carrying out adsorption treatment on active gas in the gas mixture without the organic gas, and removing the active gas to obtain a mixture which only contains the rare gas; separating the rare gas in the gas mixture one by one; and meanwhile, carrying out isotope analysis on the separated rare gas to obtain data composed of rare gas information and isotopes of the rare gas. According to the method and the online analysis system, disclosed by the invention, chemical components of the shale residual gas, rare gas composition and the isotope information thereof can be analyzed simultaneously, and all-component analysis of the shale residual gas is realized; influence factors of an analysis process are few; and the online analysis method and system have the advantages of accurate result, high efficiency, simplicity in operation and wide universality.